Radiant heat - run circulation pump 24/7?

[Blk88GT]

When I installed my radiant setup 5 years ago, I was told to run my circulation pump (Grundfos) 24/7 so that's what I did.

Looking back, I'm not sure that's what I should have done. I'm using a Lion 20KW electric boiler that has a provision to run a pump off the main control board.

Should I rewire it to be controlled by the boiler or should I leave it the way it is, running 24/7 in the winter?

I've never had any issues with it this way, but I'd hate to run it if I'm not gaining anything but extra wear on the pump.

 

[Kaizen]

Running it continually allows you to keep a lower temp by the boiler. Ones that kick off and on via thermostat controls often need higher temperature. I don't worry about my circulator life. They last for a decade or more


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[finn]

I may be dumb, but how does running water in a circle do anything to heat transfer, unless there is a heat source, ie a boiler. The water will be at the same temperature as the floor whether it’s running around in a circle or stagnant, as long as the boiler is not running.

 

[Kaizen]

I may be dumb, but how does running water in a circle do anything to heat transfer, unless there is a heat source, ie a boiler. The water will be at the same temperature as the floor whether it’s running around in a circle or stagnant, as long as the boiler is not running.

The loop circulator runs it continually and the boiler circulates to the loop/manifold when temp drops below set temp


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[yeldogt]

The constant circulation is normally done with outdoor reset -- the boiler is providing just what the floor needs to keep the room at the desired temp.

Typically -- with on off operation you need a floor thermostat. The floor thermostat turns the pump on and off. Typically higher temp water. A room thermostat will often allow the room to over shoot and the floor to get too hot.

 

[finn]

Wouldn’t the floor thermostat be a better solution than having a continuously running pump?

In any case you need some type of thermostat or switch to start the boiler.

 

[Blk88GT]

I'm using an Aube thermostat, it has a slab sensor but only for failsafe (high/low). The boiler is triggered based on air temp, not slab temp.

 

[Sureshot]

I would tape the floor sensor to the floor return line and aim to keep a consistent return water temperature.


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[Blk88GT]

Anyone else?

 

[yeldogt]

Typically the circulator is controlled by the outdoor reset .. above a temp outside the circulator will go off. It really depends on how much your boiler is actually running .. with outdoor reset the boiler is on and off maintaining the correct temp water for the current building load.

Typically, with your setup the floor heats up until the slab sensor is satisfied .. the room temp is not satisfied until the air is heated .. this can take many cycles of the floor. With many systems with only room thermostat the floor will over heat.

Do you have a tempering devise after the boiler -- what controls the boilers water temp.

Sometimes you can use the room thermostat to control the pump .. it may allow the floor to cool a bit ... it's something you have to play with. At 85 watts they are not energy killers.

 

[Blk88GT]

My boiler has an adjustable aquastat to fire additional elements to maintain the outlet temperature. Going from memory, I have mine set around 80-90F.